The present invention relates generally to a missile tracking system. More particularly, the present invention relates to a system for tracking an optical beacon located on the missile, which uses a solid state imaging array in conjunction with conventional digital processing electronics.
There are missiles, such as the TOW missile (tube-launched, optically-tracked, wire-guided missile), that do not include on-board tracking electronics. As a result, such missiles require input of target tracking information from a tracking system that i typically located on a platform (e.g., helicopter) from which the missile is launched.
Typically, such a system includes a target designator, which defines a boresight or line of sight (LOS) from the missile""s launch position to the target. The tracking system gathers information necessary to track the missile, thereby permitting a guidance system to guide the missile along this defined boresight or LOS to the target using a closed-loop control strategy. Specifically, the tracking system gathers information it uses to calculate error signals that are indicative of the relationship between the actual flight path of the missile and the LOS. As the missile moves away from the LOS, the error signals increase, and as the missile moves closer to the LOS, the error signals decrease. The tracking system uses these error signals to calculate an angular displacement measurement (i.e., angle-off-boresight) that it then outputs to a navigation or guidance system. In turn, the navigation or guidance system, in conjunction with an autopilot system, uses the angular displacement measurement in accordance with a guidance law to guide the missile down the boresight to the target.
Tracking systems generally track an optical signal generated by an optical beacon generator located on the missile. The tracking systems generally include an optical system that is used to gather image data, and generally is made up of a series of lenses or prisms that focus the image data on an array of detectors. Electronic in the tracking system process the image data focused on the array in order locate the optical signal emitting from the missile. Historically, the series of lenses or prisms have included a motor driven mirror or prism. The motor driven mirror or prism is rotated in order to xe2x80x9cscanxe2x80x9d the focused image data across an xe2x80x9cLxe2x80x9d shaped detector array, a process necessary to enable the electronics to determine the azimuth and elevation signals needed to calculate the angular displacement. Although these prior systems have proven effective, they do suffer from two main drawbacks.
First, in order to rotate the mirror or prism, the implementation requires the use of a motor and associated geartrain assembly, both of which are susceptible to wear and mechanical failure.
Second, the system requires an aperture (generally having a diameter of three inches) that may be too large for certain platforms, such as airborne platforms. The larger diameter aperture used in these systems is necessary in order to maintain an adequate Signal-to-Noise ratio for the received image signal or data, particularly at the maximum range of the missile. Specifically, because the image data is scanned across the detector array, each individual detector receives data for only a short period of time. The short dwell time on an individual detector provides limited time to integrate the image data for purposes of noise averaging. As a result, a stronger signal is needed to maintain an adequate Signal-to-Noise ratio
Accordingly, it would be desirable to have a missile tracking system that did not suffer from these drawbacks. In particular, it would be desirable to have a missile tracking system that did not require a rotating mirror or prism to scan image data across the array. Furthermore, it would be desirable to have a missile tracking system that could maintain an adequate Signal-to-Noise ratio using an aperture that had a sufficiently small diameter to make it potentially suitable for all platforms on which the tracking system may be used.
The present invention provides a missile tracking system that employs an optical system, which is stationary in relation to the detector array on which it is focusing image data. In other words, an optical path along which the image data travels is fixed between the optical system of the tracker and the detector array. Furthermore, the present invention provides a missile tracking system that can maintain an adequate Signal-to-Noise ratio using an aperture having a diameter of one to two inches.
In accordance with one aspect of the present invention, a system is provided for tracking a missile in flight, in which the missile has an optical beacon generator that outputs a modulated signal having a predetermined frequency. The tracking system includes an optical system for transmitting image data along an optical path onto an array of detectors, such that each detector in the array receives substantially simultaneously the image data from the optical system, and a means for processing the image data transmitted onto the array of detectors in order to locate the optical beacon.
In accordance with another aspect of the invention, a system for tracking a missile is provided in which the means for processing samples the image data at a first frequency during a first portion of the flight of the missile and at a second frequency during a second portion of the flight of the missile.
In accordance with still a further aspect of the present invention, a system is provided for tracking a missile in flight, in which the missile has an optical beacon generator that outputs a modulated signal having a predetermined frequency. The tracking system includes an optical system for transmitting image data along an optic path onto an array of detectors, in which the optical path remains fixed between the optical system and the array. The tracking system also includes means for processing the image data transmitted onto the array of detectors in order to locate the optical beacon.
In accordance with still another aspect of the present invention, a system is provided far guiding and tracking a missile in flight, in which the missile has an optical beacon generator that outputs a modulated signal having a predetermined frequency. This guiding and tracking system includes means for establishing an ailment for the missile and means for transmitting image data along an optical pat onto an array of detectors such that each detector receives the image data substantially simultaneously. The system also includes means for processing the image data transmitted onto the array of detectors in order to establish a position of the optical beacon relative to the aimpoint and means for guiding the missile to he aimpoint in response to the position of the optical beacon relative to the aimpoint